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The Sentinel-1 satellites prove that San Francisco Millennium Tower skyscraper is sinking by a few centimetres a year

Urban Planning

25/11/2016

Modified Copernicus Sentinel data

The 58-storey Millennium Tower in the centre of San Francisco that was completed in 2009 has recently been showing signs of sinking and tilting. Although the cause has not been pinpointed, it is believed that the movements are connected to the supporting piles not firmly resting on bedrock.

The Copernicus Sentinel-1 satellites have shown that the skyscraper is sinking by a few centimetres a year. Scientists from ESA and Geological Survey of Norway combined multiple radar scans from the Copernicus Sentinel-1 twin satellites of the same area to detect subtle surface changes – down to millimetres. The technique works well with buildings because they better reflect the radar beam.

The San Francisco study can be a benchmark for other cases. The European cities experience similar subsidence, for example, the area around Oslo’s train station in Norway is also reclaimed land. Newer buildings, such as the nearby opera house, have proper foundation into bedrock, but the older parts of the station experience severe subsidence.The studies of San Francisco and Oslo are paving the way for moving from targeted case studies to a nationwide or even continental-scale land deformation service.

The Copernicus Sentinel-1 radar twin satellites provide all-weather, day and night imagery for land and ocean services. The Sentinel-1A and Sentinel-1B were respectively launched on 3 April 2014 and on 25 April 2016.